British authorities have arrested 12 people connected to Saturday's London attacks. Just like Salman Abedi, who carried out last month's concert bombing in Manchester, the jihadis who went on this Ramadan rampage were known extremists.

It is extremely disturbing that they could pull off the London attacks, even as British authorities are still actively investigating the Manchester bombing and making arrests in that case. News broke Saturday that a 17th person had been detained in that investigation.

Moreover, the New York Times reported Saturday that Abedi met an ISIS squad in Libya that was "linked to the November 2015 Paris terrorist attack."

What is the point of "terror watch lists"? Are they nothing more than just that -- databases of known extremists that we double check names against AFTER we witness the latest attack?

It turns out that one of the jihadists involved in Saturday's slaughter had been filmed last year in a documentary about Islamic extremists in Great Britain. He had also been reported to the police several times for his extremism, including "trying to radicalize children in a local park."

By some estimates, there are at least 3,000 known Islamic extremists in Great Britain. Perhaps as many as 400 have fought for ISIS in Iraq and Syria and returned to the U.K.

Islamists who despise Western Civilization do not have to live in Western countries that value religious liberty and women' rights. The British government should begin tackling its extremism problem by immediately deporting the 400 ISIS fighters and any of the 3,000 extremists who are not British citizens.

Perry's Pearls of Wisdom

Singer Katy Perry responded to the Manchester bombing by telling her adoring fans, "No barriers, no borders, we all just need to co-exist."

She followed up on that pearl of wisdom with this gem offered at last night's benefit concert for the Manchester victims:

"It's not easy to always choose love, is it? Especially in moments like these, right? . . . But love conquers fear and love conquers hate. . . Just touch the person next to you. Make human contact. Tell them, 'I love you.' . . . I encourage you to choose love even when it's difficult."

When I read that statement, a couple of thoughts came to mind. I don't begrudge anyone trying to make 12 and 13 year-old girls feel better after what they have witnessed in their country. But let me point out the obvious: What is okay to tell 12 and 13 year-old girls is not an effective strategy to prevent more 12 and 13 year-old girls from being buried.

If entertainers, misguided clerics and university professors want to sing Kumbaya and Over the Rainbow together, they should pause to recognize that these are not songs they would be allowed to sing in large portions of the Islamic world.

The problem that the West has, particularly in Europe, is that their anti-Islamic terror policies all too often resemble a Katy Perry concert.

If you want your little boys and girls to grow up to adulthood, all of us in the West better start making adult decisions about how to remove from our midst the people who yearn to kill us.

President Donald Trump gets it. It is hard to find a European leader who does.

Celebrating Israel

Today marks the 50th anniversary of the beginning of the 1967 Six-Day War. In the days and weeks prior, vast Arab armies had mobilized on Israel's borders. On May 28, 1967, Gamal Nasser, the leader of Egypt, declared:

"We will not accept any. . . coexistence with Israel. . . Today the issue is not the establishment of peace between the Arab states and Israel. . . The war with Israel is in effect since 1948."

Four days later, President Abdul Rahman Arif of Iraq, said:

"The existence of Israel is an error which we must put right. This is our opportunity to wipe out the disgrace which is Israel which has been with us since 1948. Our goal is clear -- to wipe Israel off the map."

By this point, more than 450,000 Arab troops, 2,800 tanks and 800 aircraft had surrounded Israel. Then on the morning of June 5, 1967, the Israeli military launched a surprise offensive. In the first day of fighting, the Egyptian and Syrian air forces were largely destroyed.

The Israeli military campaign was stunningly successful. Jerusalem was liberated and reunified on June 7th and the war ended three days later.

As former Israeli Ambassador to the United States Michael Oren wrote in the New York Times:

"Israelis are celebrating 50 years since the Six-Day War -- and with good reason. That victory saved us from destruction and reunited our holiest city. Ultimately, it also brought us peace with Egypt and Jordan and a strategic alliance with the United States."